Adding python example of mouse interaction and use of correlation on an image

samples/python2/mouse_and_match.py

+#!/usr/bin/env python
+''' 
+mouse_and_match.py [-i path | --input path: default ./]
+
+Demonstrate using a mouse to interact with an image:
+ Read in the images in a directory one by one
+ Allow the user to select parts of an image with a mouse
+ When they let go of the mouse, it correlates (using matchTemplate) that patch with the image.
+ ESC to exit
+'''
+import numpy as np
+from math import *
+import sys
+import os
+import glob
+import argparse
+import cv2 as cv
+
+drag_start = None
+sel = (0,0,0,0)
+
+def onmouse(event, x, y, flags, param):
+    global drag_start, sel
+    if event == cv.EVENT_LBUTTONDOWN:
+        drag_start = x, y
+        sel = 0,0,0,0
+    elif event == cv.EVENT_LBUTTONUP:
+        if sel[2] > sel[0] and sel[3] > sel[1]:
+            patch = gray[sel[1]:sel[3],sel[0]:sel[2]]
+            result = cv.matchTemplate(gray,patch,cv.TM_CCOEFF_NORMED)
+            result = np.abs(result)**3
+            val, result = cv.threshold(result, 0.01, 0, cv.THRESH_TOZERO)
+            result8 = cv.normalize(result,None,0,255,cv.NORM_MINMAX,cv.CV_8U)
+            cv.imshow("result", result8)
+        drag_start = None
+    elif drag_start:
+        #print flags
+        if flags & cv.EVENT_FLAG_LBUTTON:
+            minpos = min(drag_start[0], x), min(drag_start[1], y)
+            maxpos = max(drag_start[0], x), max(drag_start[1], y)
+            sel = minpos[0], minpos[1], maxpos[0], maxpos[1]
+            img = cv.cvtColor(gray, cv.COLOR_GRAY2BGR)
+            cv.rectangle(img, (sel[0], sel[1]), (sel[2], sel[3]), (0,255,255), 1)
+            cv.imshow("gray", img)
+        else:
+            print "selection is complete"
+            drag_start = None
+            
+if __name__ == '__main__':
+    parser = argparse.ArgumentParser(description='Demonstrate mouse interaction with images')
+    parser.add_argument("-i","--input", default='./', help="Input directory.")
+    args = parser.parse_args()
+    path = args.input
+ 
+    cv.namedWindow("gray",1)
+    cv.setMouseCallback("gray", onmouse)
+    '''Loop through all the images in the directory'''
+    for infile in glob.glob( os.path.join(path, '*.*') ):
+        ext = os.path.splitext(infile)[1][1:] #get the filename extenstion
+        if ext == "png" or ext == "jpg" or ext == "bmp" or ext == "tiff" or ext == "pbm":
+            print infile
+            
+            img=cv.imread(infile,1)
+            if img == None:
+                continue
+            sel = (0,0,0,0)
+            drag_start = None
+            gray=cv.cvtColor(img, cv.COLOR_BGR2GRAY)
+            cv.imshow("gray",gray)
+            if (cv.waitKey() & 255) == 27:
+                break